New Eos article highlights advances in atmospheric river science and applications

9 August 2011

A feature story entitled Storms, Floods and the Science of Atmospheric
Rivers, by Marty Ralph and Mike Dettinger appears on the cover of Eos,
Transactions, American Geophysical Union, 92, No. 32, pp. 266-267, on August 9, 2011.
Eos is an international newspaper of the Earth and Space Sciences, with a
circulation of more than 61,000 researchers worldwide.

The article highlights a recent extreme case where an atmospheric river (AR) made landfall on
the west coast of California and led to extreme precipitation as the AR was
forced up and over coastal mountains. This event produced more than 410 mm
(16.5 inches) of rainfall at one site in coastal California on 14-15
October 2009. This particular AR had a very long fetch spanning most of the
North Pacific , and upon making landfall deposited >200 mm of rain along a
several-hundred-km-wide swath of coastal California (Fig. 1b). Significant
stream flow resulted, including a roughly 525 m3/s (18,600-cfs) crest and
5-m rise in water level during 12 h on Nacimiento River (Fig. 1c), along
with record high daily stream flows (for that date) at many stations in
central and northern California (Fig 1d). It should be noted that this peak
flow exceeded the annual peak flow (instantaneous) of 28 of the past 40
years, and did so in spite of the very dry conditions preceding this storm.
This event exhibits key attributes found in other extreme ARs (e.g. Neiman
et al. 2008; Ralph et al. 2011), including very large IWV values,
indications of entrainment of tropical water vapor (from the western
Pacific in this case, incorporating remnants of a west Pacific typhoon),
and the fact that it stalled over parts of the west coast in ways that
amplified the storm impacts.